FusedLocationProviderClient onLocationResult从未调用

Question

每次用户打开我的应用程序时，我都试图获取用户的位置，这是我的代码。我注意到从未onLocationResult方法被调用，并且我无法获得位置更新。谁能帮我解决这个问题？

    final LocationRequest mLocationRequest = new LocationRequest();
    mLocationRequest.setInterval(10000);
    mLocationRequest.setFastestInterval(5000);
    mLocationRequest.setPriority(LocationRequest.PRIORITY_LOW_POWER);

    LocationSettingsRequest.Builder builder = new LocationSettingsRequest.Builder()
            .addLocationRequest(mLocationRequest);

    SettingsClient client = LocationServices.getSettingsClient(this);
    Task<LocationSettingsResponse> task = client.checkLocationSettings(builder.build());

    task.addOnSuccessListener(this, new OnSuccessListener<LocationSettingsResponse>() {
        @Override
        public void onSuccess(LocationSettingsResponse locationSettingsResponse) {
            // All location settings are satisfied. The client can initialize
            // location requests here.
            // ...
            LocationCallback mLocationCallback = new LocationCallback() {
                @Override
                public void onLocationResult(LocationResult locationResult) {
                    if (locationResult == null) {
                        return;
                    }
                    for (Location location : locationResult.getLocations()) {
                        Log.d("asdffff",""+ location.getLatitude());
                        Log.d("asdffff",""+ location.getLongitude());
                    }
                };
            };
            mFusedLocationProviderClient.requestLocationUpdates(mLocationRequest,
                    mLocationCallback,
                    null /* Looper */);
        }
    });